Fuel injection system for internal combustion engine

ABSTRACT

To extend the time of opening of fuel injection valves during starting, a timing circuit, having a time constant preferably between 5 and 30 seconds, and desirably about 25 seconds, is connected to the electronic control circuit controlling the opening times of the fuel injection valves. The timing circuit provides a decreasing signal to extend the time during which the injection valves are open from the time the starter switch is operated. Preferably, the fuel injection system includes a pulse duration multiplier circuit, having a multiplication factor varying between 1 and 5, and the timing circuit affects the multiplication factor.

United States Patent 1 Glockler et al.

[ 51 May 22, 1973 [54] FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTIONENGINE [73] Assignee: Robert Bosch G.m.b.H., Stuttgart,

Germany [22] Filed: Dec. 17, 1970 [21] Appl. No.: 99,139

[30] Foreign Application Priority Data 3,628.510 12/1971 Moulds ..123/32EA 2,981,246 4/1961 Woodward. .......123/32 EA 3,032,025 5/1962 Long..123/32 EA 3,483,851 12/1969 Reichardt.... 123/32 EA 3,500,803 3/1970Long ..123/32 EA 3,504,657 4/1970 Eichler et a1 ..l23/32 EA PrimaryExaminer-Laurence M. Goodridge Assistant Examiner-Cort FlintAttorney-Flynn & Frishauf [57] ABSTRACT To extend the time of opening offuel injection valves during starting, a timing circuit, having a timeconstant preferably between 5 and 30 seconds, and desirably about 25seconds, is connected to the electronic control circuit controlling theopening times of the fuel injection valves. The timing circuit providesa decreasing signal to extend the time during which the injection valvesare open from the time the starter switch is operated. Preferably, thefuel injection system includes a pulse duration multiplier circuit,having a multiplication factor varying between 1 and 5, and the timingcircuit affects the multiplication factor.

1 1 Claims, 4 Drawing Figures PATENIEUHMTZZESH 3.734067.

INVENTORS Qtto GLOCKLER 1 =t HermcmnSCHMlD 31 n3 Dieter EICHLER theirATTORNEY FUEL INJECTION SYSTEM FOR INTERNAL COMBUSTION ENGINECross-reference to prior patents: U. S. Pat. No. 3,483,851.

The present invention relates to fuel injection systems for internalcombustion engines and more particularly to the fuel injection system inwhich electromagnetically operating in fuel injection valves have thetime of opening of the valve controlled in accordance with operatingparameters of the engine. A complete operating system of this type isdisclosed in U.S. Pat No. 3,483,851, to which reference is hereby made.

Fuel injection systems of the type to which the invention relates havean injection valve which is opened by essentially square electricalpulses occuring synchronously with the rotation of the cam shaft. Thepulse duration, corresponding to the opening time of the valve iscontrolled by a controlsystem in dependence on at least one operatingparameter of the internal combustion engine, for example intake manifoldpressure (or, rather, vacuum). Other operating parameters mayadditionally control the opening time, such as temperature of theengine. The amount of fuel injected to each cylinder during the suctionstroke thereof, by fuel injection systems of this type, can beaccurately matched to the operating conditions of the engine, andspecifically to its speed and the load thereon. This has the advantagethat the exhaust gases from the internal combustion engine can beminimized, and operating efficiency of the engine increased. Normally,the tuning of the engine, that is the adjustment of the fuel-air mixtureis made with respect to the engine at its normal operating temperature,that is, when the engine has operated for some time and has reached astable temperature as determined by its cooling system. Upon coldstarting of an internal combustion engine, ease of start can be insuredonly when the amount of fuel supplied to the cylinder during the suctionstroke is substantially increased, that is, when the engine receives aricher mixture with respect to the mixtures which are necessary anddesirable when the engine has reached its normal operating temperature.

Various fuel injection arrangements, and particularly gasoline injectionarrangements have been proposed in which a temperature sensing device isarranged in heattransfer relationship to the internal combustion engine.The temperature sensor controls the ratio of fuel to air during theoperationof the internal combustion engine, and particularly uponstarting, that is, effectively in the period when the engine is cold anduntil it reaches its normal operating temperature. The fuelair ratio isincreased until the normal operating temperature is reached. Such anelectronic control arrangement has a circuit including an inputtransistor andan output transistor, and a capacitative, or inductivefeedback circuit which forms an energy or charge storage device. Theduration of the pulses controlling the opening of the injection valve,or valves is then determined by electrical parameters such as voltagesand currents, and stored energy, which change in dependence on operatingparameters of the internal combustion engine, such as air temperature,pressure (vacuum) in the intake manifold, and speed, for example. Aknown control system utilizes a highly temperature-responsive resistancewhich is in thermal transfer with the engine cooling water, or,respectively, with its cylinder head. The temperature sensitiveresistance has either a positive or negative temperature coefficient andis arranged in the collector circuit of the output transistor of acontrolled multivibrator in the electronic control system. Other knowncontrol systems use a first control multivibrator generating pulsessynchronized with the speed of the engine, connected to a multiplicationstage which increase the length of the base pulses derived from thecontrol multivibrator by a factor depending on temperature (and, ifdesired, on other operating parameters) which, together with the basepulse, provides an overall injection pulse to control the injectionvalves.

Upon investigation of the starting process in large numbers of varioustypes of internal combustion engines, it has been found that they allrequired a substantially richer mixture upon cold starting and idling,to maintain the engine in operation, and to prevent stalling, or evenrecurring stalling. The richer mixture is also required to insure goodresponse to sudden increases in fuel mixtures, for example commanded bythe vehicle operator. It has been found, however, that only a very shortoperating period of the motor is required before such a rich mixture isno longer necessary; for example, in some motors the time may be asshort as 5 seconds, whereas in others it may be 30 seconds or evenlonger; in many engines the time after which a substantially enrichedmixture is no longer required is in the order of 25 seconds. in thattime the excess fuel can be reduced by 50 percent. If,however, theinternal combustion engine continues to operate with the enrichedstarting mixture, even short-time operation under these conditionscauses carbon disposits on the spark plugs and misfire, or completeignition malfunction. Additionally, an excessively high portion of rawfuel will be found in the exhaust of the internal combustion engine. Byswitch-over of the control arrangement within the time period of fromabout 5 to about 30 seconds to much lower fuel quantity of the fuelbeing injected, objectionable exhaust and ignition malfunctions can beavoided.

It is accordingly an object of the present invention to provide a fuelinjection system for internal combustion engines in which the fuel-airratio is decreased upon starting, and then smoothly increased to normaloperating values during the time required for the engine from cold startto reach normal idling running conditions, typically within about 5 to30 seconds or so.

Subject matter of the present invention: Briefly, a timing circuit isprovided, preferably controlled by the starter switch, which during thetime period required by the engine to reach normal running conditions,after cold start, increases the pulse period of fuel injection pulsesapplied to fuel injection valves. This time period may be between 5 and30 seconds, or longer, and preferably is about 20-25 seconds.

A timing circuit which changes the amount of fuel injected, afterstarting, from a rich mixture to a normal, operating or leaner mixturecan be constructed in various ways to operate, for example,electrically, electronically, thermoelectrically or mechanically, andalso hydraulically or pneumatically. Change-over of fuel-air ratio froma richer to a leaner mixture may be controlled by the starting switchitself, and may control the amount of mixture smoothly, that isprogressively from a richer to a leaner mixture, or in one or moreabrupt steps. It is important, however, that the pulse durationcontrolling the opening of the fuel injection valves varies from alonger opening period, upon starting, to the opening period required byengine normal operation.

Progressive decrease of the fuel-air ratio to increase the ratio from ahigh value to a normal operating value can be easily controlled in fuelinjection systems having a pair of multivibrators; each providing avalve opening pulse. The first provides a base pulse, which, in turn,triggers a second, which forms a multiplication stage generating asecond pulse the time duration of which is that of the base pulse,multiplied by a factor varying between and 5. In such an arrangement,the timing circuit can be directly connected to the multiplication stageto affect the multiplication factor thereof, and to increase this factorupon starting, and then progressively decrease the factor as the timeafter starting elapses.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of a fuel injection system incombination with an internal combustion engine;

FIG. 2 is a timing diagram illustrating the effect of the timingcircuit;

FIG. 3 is a modified form of timing circuit and FIG. 4 is anotherembodiment of a timing circuit.

The fuel injection system will be described in connection with a fourcylinder engine 11, having spark plugs 12, connected to an ignitionsystem, not shown. Fuel injection valves 14 are located in the inletmanifold stubs 13 leading to the various cylinders from the inletmanifold. The injection valves 14 are placed next to the inlet valves.Each injection valve 14 is supplied with fuel over a line 15 connectedto a fuel distribution unit 16. Fuel is pumped into line 15 by a pump 7,driven for example by an electric motor, and supplying fuel underpressure, controlled by a pressure regulator 18 at approximately 3 At (2At gauge).

Each one of the injection valves 14 has a magnetization winding, orsolenoid coil, one end of which is connected to chassis, and the otherend of which is connected to a line 19 and over a resistance, 20, eachto the electronic fuel supply control circuit. In the example shown, allfour valves are simultaneously operated, in synchronism with therotation of the crank shaft, respectively. An opening pulse I, (FIG. 2),having a time duration which determines the opening time of the valvesis applied from an output power stage 22 (FIG. 1) to the fuel injectionvalve.

The electronic control system, essentially, is formed ofa mono-stablemultivibrator 25, an inverter stage 26, a multiplication stage 2, and anOR gate 28 to which the output or power stage 22 is connected.Additionally, and in accordance with the present invention, a timingcircuit 30 is provided, connected to the multiplication stage.

Multivibrator 25 includes an input and an output transistor 31, 32. Thebase of transistor 32 is connected to the collector of the inputtransistor 31. The collector of the output transistor 32 is connected toa common positive bus 33 over primary winding 35 of a transformer 36,having a movable core 37. Core 37 is connected over a linkage,schematically indicated by a chain-dotted line 38, to the membrane of apressure transducer 39. Pressure transducer 39 is sensitive to pressure(or rather, vacuum) in the intake manifold of the internal combustionengine, and is located in the manifold behind air inlet 41, and athrottle valve, the

position of which is controllable by accelerator pedal 40.

Input transistor 31 of the multivibrator 25, under normal operatingconditions, is held in conductive state by resistance 43 connecting thebase thereof to the positive bus. Additionally, the base is connected bydiode 44, to the other winding 45 of transformer 36; the other terminalof winding 45 is connected to the tap point of a voltage divider formedof resistances 46, 47.

The mono-stable multivibrator 25 changes state in synchronism with therotation of the engine, for example in synchronism with the crank shaftthereof. A cam 51, applied to the cam shaft of the engine operates aswitch 53 which is connected to chassis. The switch contact 54 isconnected to a charge resistance 55 and to one electrode of a couplingcondenser 56. The other electrode of the condenser is connected over asecond charge resistance 57 with the chassis bus 52, and, additionally,over a diode 58 with the base of the input transistor 31.

So long as switch 53 is in the position shown in the figure, that is, isopen, then condenser 56 can charge over the two resistances 55 and 57,each connected to a respective supply bus 33, 52, to the operatingvoltage of the system. When switch 53 is pressed against the contact 54by the control cam 51, the positively charged electrode of condenser 56is connected to the negative potential, or chassis; the base oftransistor 31 will receive a strongly negative pulse and transistor 31will block. This brings the output transistor 32 into conductivecondition. The collector current flowing over primary winding 35 oftransformer 36 induces a voltage in the winding 45 which can furthercontrol input transistor 31 to remain conductive, the duration of theblocking voltage depending on the pressure (or rather vacuum) within theintake manifold of the internal combustion engine. If the pressure issubstantially below atmospheric pressure, due to closed or almost closedposition of the valve, the pressure transducer 39 will lift the core 37in the direction indicated by the arrow, thus increasing the air gap inthe transformer 36, so that the inductivity of the primary winding 35 issubstantially decreased. Since the input transistor 31, due to the lowinduced voltages will rapidly return to its ordinary, conductivecondition, the output transistor 32 will be blocked. Thus, the basepulse I, appearing at the collector of the output transistor will haveonly a very short duration, for example. 1.2 msec., however, if pedal 40is operated and the valve in the intake line is open, the pressurebehind the valve flap will deviate only little from that of ordinaryatmospheric pressure, even at high speed. This causes the iron core 37to be lifted only slightly, increasing the inductivity of primarywinding 35 and causing only slow rise of the collector current fromtransistor 32 in the primary winding. This increases the pulse period ofthe base pulse I, to about 4.2 msec.

In the example illustrated, each base pulse I is transmitted from theoutput transistor 32 to an inverter state 26 and then to a multiplyingstage 27. The multiplying stage 27 generates an extension pulse I,following immediately after the base pulse 1,. The duration of theextension pulse I, bears a relationship to the base pulse in that it isa multiplied value of the length of the base pulse. The multiplicationfactor can be determined in know manner (see the above referred topatent) in dependence on various operating conditions and parameters ofthe internal combustion engine, for example cooling water temperature.

The multiplying stage includes a storage condenser 60, a chargingtransistor 61 and a discharge transistor 62. A switching transistor 63has its emitter directly connected to the chassis bus 52. The basethereof is connected to a resistance 64, which in turn connects to thechassis bus 52, and to one electrode of storage condenser 60. Storagecondenser 60 is connected, in turn, to the collector of the chargingtransistor 61. The discharge transistor 62 has its base connected to thetap point of a voltage divider formed of resistances 65, 66 connectedacross the supply buses 52, 53. The emitter of transistor 62 isconnected over a resistance 67 to the positive bus 33. The chargingtransistor 61 has its collector connected through the other electrode ofcharging condenser 60. Transistor 61 is connected as an emitterfollower, since its emitter is connected over emitter resistance 69 tothe positive bus 33; its base is connected to a junction X, whichdirectly connects to the collector of transistor 70 of the inverterstage 26. Junction X, and hence the collector of transistor 70 isconnected over a resistance 73 to positive bus 33. The base of theinvertor transistor 70 is connected over the resistance 72 with thecollector of output transistor 32; and, over a resistance 71 to thechassis bus 52.

Junction X, and hence the collector of transistor 70 is connected over acoupling resistance 76 to a transistor 75, forming part of the OR Gate28. The base of transistor 75 additionally is connected over resistance77 to chassis bus 52. The second coupling resistance 78 connects thebase of the OR Gate transistor 75 with the collector of switchingtransistor 63 forming part of the multiplying stage 27. The collector oftransistor 75 is connected to the common positive line 33 by means of aresistance 79. Its emitter is connected to the chassis bus 52 overresistance 80. The base of npn transistor 81 is connected to the emitterof transistor 75, and forms, together with transistor 82 the outputpower stage 22.

Operation: the circuit so far described is known in principle, and itsgeneral operation can therefore be described briefly. When the internalcombustion engine rotates, cam 51, upon each revolution, closes switch53 and the normally conductive input transistor 31 will block. Thiscauses generation of the base pulse 1, the duration of which will dependon the speed of rotation of the engine and the position of the flap ofthe valve as commanded by pedal 40. During the time of this base pulse1,, the normally conductive transistor 70 of stage 26 will block, sothat transistor 75, forming part of the OR Gate 28 will becomeconductive over the coupling resistance 76. This causes conduction oftransistor 81 and of power transistor 82. Collector potential ofcharging transistor 61, just like the collector potential of theinverter transistor 70, which will be conductive, will be approximatelyat the same value as that of chassis, line 52. The voltage U across thestorage condenser 60 will be effectively zero.

As soon as the base pulse 1,, starts, the base potential of the chargingtransistor 61 will reach a voltage value which is somewhat intermediatethe voltage of the positive line 33 and of chassis bus 52, due to thebase current of OR Gate transistor 75 flowing over resistance 73.Charging transistor 61 can thus supply a constant charging current forstorage condenser 60. During the period of the base pulse I voltage U onthe storage condenser 60 will rise linearly, as indicated in FIG. 2 inthe time period between t, to t At point t the base pulse 1,,terminates. As soon as inverter stage transistor becomes conductive,that is, at the termination of the base pulse, the collector thereofwill receive a strongly negative potential and therefore also thecollector of charging transistor 61. Thus, the charge on the storagecondenser 60 will cause switching transistor 63 to block, by applying astrongly negative potential to its base. This blocking period will befor such a time until a charge has dissipated over discharge transistor62. Transistor 62 insures that the discharge current will have aconstant value. As seen in FIG. 2, the discharge period will extend fromtime t to time t;,, at which point the switching transistor 63 willagain become conductive. During this blocked condition of switchingtransistor 63, OR gate transistor is kept conductive over the secondcoupling resistance 78 and the collector resistance 68. Thus, the pulseI, is added to the pulse I so that a combined opening pulse 1, isprovided, the time duration of which controls the amount of fuel beinginjected.

The factor f (T,,/T,,) has a variable value, varying between zero and 5,when the internal combustion engine is at operating temperature;according to practical experience, f l. T, is the duration of theextension pulse 1,, and T, is the duration of the base pulse 1,, of thefirst multivibrator 25.

It is desired to supply more fuel to the internal combustion engineimmediately after starting, than the amount of fuel which would benecessary after continued operation. To provide such additional fuel, inaccordance with the invention, timing circuit 30 is provided whichelectronically increases the above referred extension factor f ofmultiplier stage 27 during the time period until the engine reachesnormal operating equilibrium, typically about 20-25 sec. The multiplyingfactor is substantially increased initially, and progressively decreasesto the value proper for continuous operation of the engine during theperiod for which the timing circuit is set. Thereafter, the factor f ismaintained. Thus, the extension of the pulse by a multiplying factor issolely dependent on time and not on any other operating or ambientparameter of the engine.

The timing circuit 30 has two npn transistors 85, 86. During normaloperation, both transistors are blocked and, to keep them blocked, thebase of the first transistor 85 is connected over a resistance 88 to thechassis bus 52; the emitter of transistor 86 is directly connected tochassis'bus 52, and its space to the emitter of transistor 85 and,further, over a resistance 87 to chassis bus 52. A condenser 89interconnects tthe collector of transistor 86 to the base of transistor85; the condenser has a value of about 3 pF. Resistance 90 connects thecollector of transistor 86 to the positive bus 33, and resistance 93 isthe collector resistance for transistor 85. A limiting resistance 91, inseries with a diode 92 connects from the connector of transistor 86 tojunction X of the inverter stage'26, and thus with the collector oftransistor 70 and the base of charging transistor 61. The base of thefirst timing circuit transistor 85 is connected over a resistance 94with starter switch 96 which, in turn, has one terminal connected topositive bus 33. The other terminal of starter switch 96 is connectedwith a point P at the end of the solenoid winding 97 of the usualstarter relay, not further shown. Upon operation of switch 96, winding97 is energized and starts the starter motor. A diode is connectedbetween resistance 94 and the base of transistor 85, and a resistance 98connects between the diode 94 and resistance 94 to the chassis bus 52.

To start the engine, starter switch 96 is closed. First transistor 85,over resistance 94 and diode 95, will have base current applied and willbecome conductive, simultaneously causing transistor 86 to becomeconductive. The condenser 89, before starting, charged to approximatelyfull operating voltage, now discharges since, in conductive condition,the second transistor 86 has a collector voltage which is close to thatof the chassis bus 52. Since resistance 91 is also almost at chassisvoltage, a substantially higher charging current will flow throughcharging transistor 61 as soon as transistor 70 changes to blockedcondition at the next base pulse 1,. During starting, a series ofextension pulse I, result, causing a corresponding increase of theinjection periods, to facilitate starting of the engine. In a practicalexample, factorf= at a base pulse time of 2.5 msec., so that a totalpulse of duration T, of msec. is provided for each fuel injection.

The form of the time switch 30 is so selected that, after opening of thestarter switch 96, and for a period of time of approximately seconds,prolongation factorf of multiplication circuit 27 is held substantiallyabove the value necessary for constant operation. Under normaloperation, this value is approximately f, is equal to I It is regulatedfrom its high initial value off 5 progressively to the operating valueoff I. As soon as the button of switch 96 is released, both transistors85, 86 have the tendency to return to their initial blocked condition,so that the capacitor 89 which is discharged after closing, upon openingof the switch, will revert to its normal, fully charged condition. Thisrequires a charging current indicated by I FIG. 1, which, essentially,is formed by the quotient of the sum of the emitter-base voltages of thetransistors, 85, 86, as well as of the resistance 88. This chargingcurrent is substantially constant. As a result, the voltage at thecollector of transistor 86 rises linearly and, only after thepredetermined time period of, for example, 20 seconds, will reach avalue in which diode 92 transfers to blocked condition. The voltage,rising in positive direction on the base of the charge in transistor 61will cause a decrease in the charging current for the charge incondenser 60 developed by transistor 61. As is clearly apparent from thecircuit diagram, FIG. 1, and the foregoing explanation, the timingperiod of the timing circuit and thus the extension, or multiplicationfactor (f) is dependent only on the electrical values of the timingcircuit. The timing period is independent of any other effects, oroperating or ambient parameters.

As a result, voltage U, across condenser 60 will rise more slowly, afterreleasing switch 96 upon occurrence of the next base pulse l,,, than inthe preceding base pulses. Assuming the impulse length of the base pulseis to remain constant, the discharge time is also correspondinglydecreased and the prolongation factor f decreases. As seen in FIG. 2,the base pulse starting at time will cause a pulse terminating at time rcorresponding to a normal value of a multiplication factor which isapproximately equal to I. This will occur after a predetermined periodof time, in the example after about 20 seconds, with a sufficient timelag to enable steady state operation of the internal combustion engineafter starting. The scale in FIG. 2, indicative of time values, ishighly compressed for illustration.

In actual operation, an idling speed of about 600 rpm, corresponding to10 rpsec. would cause, during these 20 seconds, approximately 200injections cycles, the time duration of the various individualinjections of fuel decreasing with progressive decrease of theprolongation factor f.

The circuit 30 shown in FIG. 1 is a preferred embodiment, having theadvantage that the time period of delay, in this case 20 seconds, isindependent of the speed of the engine, and the pulse duration of thebase pulses I FIG. 3 illustrates a timing circuit which is much simplerand, in principle consists of a transistor Tr having its emitterconnected to the chassis bus 52, a collector resistance R,, and acondenser C interconnecting the collector and the base. A pair of baseresistances R and R are further provided. Resistance R interconnects thebase with the negative bus 52. Resistance R forms a connection of thebase of the transistor T to the connecting point P between the winding97 of the starting relays and of starting switch 96. In order to avoidoverloading the base junction of the transistor T, by voltage peakswhich could arise after starting upon opening of switch 96, a bypassdiode D is provided between junction point P and the negative bus 52.The output is again coupled from the collector over resistance 91 anddiode 92 to junction X.

FIG. 4 illustrates a timing circuit which is only slightly differentfrom that of FIG. 1. It differs essentially in that the collectorresistance 90 of transistor 86 is missing. This enables decrease of thecapacity of the condenser 89, interconnected between the base oftransistor and the collector of transistor 86, to about one tenth of thevalue required for the condenser in accordance with FIG. 1. A typicalvalue would be 0.3 uF. The timing provided by the circuit of FIG. 4 isapproximately 20 seconds; in contrast to the circuit of FIG. 1 it is,however, speed dependent and further dependent on the length of the basepulse s I,,, since, for discharge of the condenser 89, a balancingcurrent is only available if the transistor 70, forming part of theinverter stage is blocked during a base pulse 1,.

The circuit operates entirely automatically and independently of anycontrols required by the operator of the vehicle of which the engine mayform a part; it provides for reliable starting, even upon cold engineconditions.

We claim:

1. Fuel injection system for internal combustion engines having meanscontrolling the injection of fuel comprising at least one electricallyoperated fuel injection valve;

electrical means synchronized with the rotation of the engine generatingelectrical pulses, connected to said valve, to open the valve;

control means including means generating a base pulse (I,,) having adetermined pulse length and a multiplying stage generating an extensionpulse (1,), said extension pulse being longer than said base pulselength by a multiplying factor (f) of from 1 to 5 and controlled by anoperating parameter of the engine connected to said electrical means andcontrolling the length of said pulses;

an electrical starting control means including a starter switch;

a timing circuit having a fixed predetermined timing period regardlessof engine temperature and connected to said starting control means (30)to start the timing period upon actuation of said starter switch andconnected in circuit with said control means to affect the multiplyingfactor of said multiplying stage and to increase the multiplying factorduring said fixed predetermined timing period upon starting to therebyprolong the pulses upon starting of the engine.

2. System according to claim 1, wherein the timing circuit has a timingperiod in the order of from about -3O seconds.

3. System according to claim 1, wherein the timing circuit has a timingperiod in the order of about -25 seconds.

4. System according to claim 3, wherein the starter switch isinterconnected with said timing circuit to apply a voltage to saidcircuit during operation of the starter switch.

5. System according to claim 1, wherein said timing circuit provides avariable control signal to said control means to continuously reduce theduration of the extension pulses generated by the multiplication stagefrom a prolonged period immediately upon starting, until the pulseduration is determined solely by said operating parameters when saidpredetermined period has elapsed.

6. System according to claim 1, wherein said timing circuit comprises atransistor (T means holding said transistor in blocked condition;

means (R3) interconnecting the starter switch with the base of thetransistor;

and a capacitor (C) connected in the transistor circuit between thecollector and another electrode thereof.

7. System according to claim 1, wherein a source of supply (33, 52) isprovided;

said timing circuit comprises first and second transistors (85, 86) ofsimilar conductivity type;

a resistance (87 interconnecting the emitter of one transistor (85) toone supply source terminal (52) and a resistance (93) interconnectingthe collector of said one transistor (85) to the other supply sourceterminal (33);

a base resistance (88) connected from the base parallel to the emitterresistance (87) to the respective terminal of the supply source andholding said one of said transistors (85) in'normally blocked state;

means (94, 95) interconnecting the base of said normally blockedtransistor (85) to the starter switch (96); and

a capacitor (89) connected with one terminal to said switch-transistorinterconnection means, the other terminal of said capacitor beingconnected to the collector electrode of the other transistor (86).

8. System according to claim 7, wherein said multiplying stage has acharging transistor (61) and a capacitor (60) having one terminalconnected, in series, with the emitter-collector path of the chargingtransistor (61);

a discharge transistor (62) connected to the other terminal of thecapacitor (60);

and means interconnecting the collector of said second transistor (86)of the timing circuit (30) to the base of the charging transistor (61)to increase the charging current to said charging transistor, and thusthe pulse length of said extension pulse, upon conduction of said secondtransistor (86), as determined by the state of conduction of said firsttransistor 9. System according to claim 1, wherein said timing circuitcomprises a capacitor (89); a constant current supply circuit, andswitching means being connected to affect a charge on the capacitor (89)upon closing of the starter switch and means applying a current independence on the change of charge of said capacitor (89) to saidmultiplying stage and affecting the multiplying factor thereof.

10. System according to claim 1, wherein said control means comprises afirst capacitor (60); means (61, 62) controlling the charging rate ofsaid first capacitor; and said timing circuit (30) includes switchingmeans (85, 86; T,) and a further capacitor (89; C), said switching meansinterconnecting said further capacitor with said first capacitor (60) toaffect the change of charge on the total capacitance in circuit withsaid control means upon operation of said switching means as determinedby operation of the starter switch (96).

11. System according to claim 10, wherein said switching means comprisesat least one transistor connected to be normally blocked, and to becomeconductive upon operation of said starter switch (96);

said transistor being interconnected with said further capacitor (89) toprovide a discharge path for said further capacitor (89) upon change ofsaid transistor to conductive state, and to extend the time during whichsaid means controlling the charge rate of said first capacitor (60)provides charging current.

1. Fuel injection system for internal combustion engines having meanscontrolling the injection of fuel comprising at least one electricallyoperated fuel injection valve; electrical means synchronized with therotation of the engine generating electrical pulses, connected to saidvalve, to open the valve; control means including means generating abase pulse (In) having a determined pulse length and a multiplying stagegenerating an extension pulse (Iv), said extension pulse being longerthan said base pulse length by a multiplying factor (f) of from 1 to 5and controlled by an operating parameter of the engine connected to saidelectrical means and controlling the length of said pulses; anelectrical starting control means including a starter switch; a timingcircuit having a fixed predetermined timing period regardless of enginetemperature and connected to said starting control means (30) to startthe timing period upon actuation of said starter switch and connected incircuit with said control means to affect the multiplying factor of saidmultiplying sate and to increase the multiplying factor during saidfixed predetermined timing period upon starting to thereby prolong thepulses upon starting of the engine.
 2. System according to claim 1,wherein the timing circuit has a timing period in the order of fromabout 5-30 seconds.
 3. System according to claim 1, wherein the timingcircuit has a timing period in the order of about 20-25 seconds. 4.System according to claim 3, wherein the starter switch isinterconnected with said timing circuit to apply a voltage to saidcircuit during operation of the starter switch.
 5. System according toclaim 1, wherein said timing circuit provides a variable control signalto said control means to continuously reduce the duration of theextension pulses generated by the multiplication stage from a prolongedperiod immediately upon starting, until the pulse duration is determinedsolely by said operating parameters when said predetermined period haselapsed.
 6. System according to claim 1, wherein said timing circuitcomprises a transistor (Tr); means holding said transistor in blockedcondition; means (R3) interconnecting the starter switch wiTh the baseof the transistor; and a capacitor (C) connected in the transistorcircuit between the collector and another electrode thereof.
 7. Systemaccording to claim 1, wherein a source of supply (33, 52) is provided;said timing circuit comprises first and second transistors (85, 86) ofsimilar conductivity type; a resistance (87) interconnecting the emitterof one transistor (85) to one supply source terminal (52) and aresistance (93) interconnecting the collector of said one transistor(85) to the other supply source terminal (33); a base resistance (88)connected from the base parallel to the emitter resistance (87) to therespective terminal of the supply source and holding said one of saidtransistors (85) in normally blocked state; means (94, 95)interconnecting the base of said normally blocked transistor (85) to thestarter switch (96); and a capacitor (89) connected with one terminal tosaid switch-transistor interconnection means, the other terminal of saidcapacitor being connected to the collector electrode of the othertransistor (86).
 8. System according to claim 7, wherein saidmultiplying stage has a charging transistor (61) and a capacitor (60)having one terminal connected, in series, with the emitter-collectorpath of the charging transistor (61); a discharge transistor (62)connected to the other terminal of the capacitor (60); and meansinterconnecting the collector of said second transistor (86) of thetiming circuit (30) to the base of the charging transistor (61) toincrease the charging current to said charging transistor, and thus thepulse length of said extension pulse, upon conduction of said secondtransistor (86), as determined by the state of conduction of said firsttransistor (85).
 9. System according to claim 1, wherein said timingcircuit comprises a capacitor (89); a constant current supply circuit,and switching means being connected to affect a charge on the capacitor(89) upon closing of the starter switch (96); and means applying acurrent in dependence on the change of charge of said capacitor (89) tosaid multiplying stage and affecting the multiplying factor thereof. 10.System according to claim 1, wherein said control means comprises afirst capacitor (60); means (61, 62) controlling the charging rate ofsaid first capacitor; and said timing circuit (30) includes switchingmeans (85, 86; Tr) and a further capacitor (89; C), said switching meansinterconnecting said further capacitor with said first capacitor (60) toaffect the change of charge on the total capacitance in circuit withsaid control means upon operation of said switching means as determinedby operation of the starter switch (96).
 11. System according to claim10, wherein said switching means comprises at least one transistorconnected to be normally blocked, and to become conductive uponoperation of said starter switch (96); said transistor beinginterconnected with said further capacitor (89) to provide a dischargepath for said further capacitor (89) upon change of said transistor toconductive state, and to extend the time during which said meanscontrolling the charge rate of said first capacitor (60) providescharging current.